Activities
The IMR Post Doc and NERSC Post Doc and personnel from the other work
packages will synthesize and quantify the observed and modelled interannual
variability of dense water production modes in the entire region of interest,
using the model formulations arrived at from achieved process understanding.
Results of these activities will be fed into the NOClim
project office which will take special responsibility to ensure that consistent
synthesis reports for the public are produced. This applies in particular
for connections to studies of the meridional overturning in the North
Atlantic - Nordic Seas.

Discussion, description and motivation:
It is an open question if and on which time scales formation of intermediate
to deep waters at high latitudes is one of the controlling mechanisms
for the large-scale ocean circulation, and then in particular for the
Atlantic Thermohaline Circulation.

In this work package, a synthesis will be made to qualitatively and quantitatively
construct time series of the volume flux and thermodynamic properties
associated with formation of intermediate to deep water masses in the
open Greenland Sea, along the Polar-Atlantic fronts in the northern Norwegian
Sea, and on the Barents Sea shelves. The synthesis will cover the period
of instrumental data, starting with the pioneering work of Helland-Hansen
and Nansen in the beginning of the 20th century. All of the available
observations will be used, including a unique data set of 130.000 hydrographic
stations from Russia that is not included in the World Ocean Database
(the data set is available at NERSC through collaboration with the Arctic
and Antarctic Research Institute in St. Petersburg, Russia).

Furthermore, analyses of the available observations will be bridged by
basin scale numerical ocean modelling. Three model tools will be used:
A global version of the isopycnic coordinate ocean model MICOM with fully
dynamic-thermodynamic sea ice. This model will be set up with a stretched
horizontal grid with a typical resolution of about 20-by-20 km in the
Nordic Seas. The model will be forced with daily re-analyses fields for
the period 1948 to present. Existing simulations indicate that the model
is able to describe the gross features of the ocean climate variability
in the region. Secondly, a regional, high-resolution (few km) version
of the ocean model ROMS will be applied to simulate the open ocean mixing
and the shelf processes in the region. The global MICOM model will provide
temporally and spatially consistent lateral boundary conditions for the
regional ROMS model. Finally, a 500 years control integration and a 250
years scenario integration with the Bergen Climate Model will be analysed
to assess the natural variability modes, possible changes in the characteristics
of the modes as the human-induced greenhouse warming continues, and the
role that formation of intermediate to deep waters in the Nordic Seas
have on the Atlantic Thermohaline Circulation.